Solar cell and fabrication method thereof

This application is a continuation-in-part of International Application No. PCT/CN2022/092291, filed on May 11, 2022, which claims priority to Chinese Patent Application No. 202111644240.1, filed on Dec. 29, 2021. The disclosures of the aforementioned applications are incorporated herein by reference in their entireties.

The present disclosure relates to the field of solar cell technologies, and in particular, to a solar cell and a fabrication method thereof.

At present, in existing solar cell structures, back-contact solar cells have higher photoelectric conversion efficiency since a front surface of each of the back-contact solar cells is not blocked by electrodes. P-type regions and N-type regions are arranged on different regions of a back surface of each of the back-contact solar cells, and a positive electrode and a negative electrode are then respectively arranged on each of the P-type regions and each of the N-type regions. In addition, this solar cell without blocking on the front surface is more aesthetically pleasing in addition to having high photoelectric conversion efficiency. Besides, it is easier to assemble an all-back electrode module. An interdigitated back contact (IBC) solar cell is one of existing technical directions for realizing highly efficient crystalline silicon solar cells.

However, a structure of the IBC solar cell is relatively complicated, and a fabrication method of the IBC solar cell is also relatively complicated with relatively high costs.

For the foregoing problems, the present disclosure provides a solar cell and a fabrication method thereof. In some implementations, a P-type region of the solar cell includes two P-type doped layers instead of a single P-type doped layer, which can reduce the time and complexity of forming the P-type region. For example, a bottom P-type doped layer (e.g., the P-type doped layer closer to a substrate of the solar cell) can be formed using a slower deposition method, e.g., low pressure chemical vapor deposition (LPCVD) with lower temperature and lower gas flux rate, so that the crystallization rate of the formed semiconductor layer can be high. The bottom P-type doped layer can have good passivation effect, which can reduce parasite absorption of the solar cell, especially for double-sided solar cells, where P-type doped layer and the N-type doped layer are arranged on different sides of the solar cell. A top P-type doped layer (e.g., the P-type doped layer further away from the substrate of the solar cell) can be formed using a faster deposition method, e.g., LPCVD with higher temperature and higher gas flux rate, so that the top P-type doped layer can have a lower crystallization rate. As such, a solar cell having two P-type doped layers can be fabricated faster than a solar cell having a single P-type doped layer, while quality and efficiency of the solar cell are maintained or enhanced.

In some implementations, patterning needs to be performed only once to complete fabrication of doped semiconductors in two regions. In addition, doped regions fabricated by using this method have passivated contact structures at both electrodes, bringing a good passivation effect and greatly reducing a recombination rate in metal regions, thereby improving the efficiency of the solar cell.

The present disclosure provides a fabrication method of a solar cell, including:

Further, a first semiconductor layer is formed on the first surface of the semiconductor substrate, and the first dopant is diffused into the first semiconductor layer to form the first doped layer, or the first doped layer is formed on the first surface of the semiconductor substrate through in-situ doping; and

a first auxiliary layer is formed on the surface of the side of the first doped layer facing away from the semiconductor substrate, and etching is then performed on a part of the first auxiliary layer and the first doped layer, to complete patterning and retain the part of the first doped layer.

Further, the second doped layer is formed, through in-situ doping, on the surface of the side of the first doped layer facing away from the semiconductor substrate and on the first surface of the semiconductor substrate not covered by the first doped layer; and

heating treatment is performed on the second doped layer on the first doped layer, to diffuse the first dopant in the first doped layer into the second doped layer on the first doped layer, and the second dopant in the second doped layer is also diffused into the first doped layer, to transform the second doped layer on the first doped layer into the third doped layer.

Further, the heating treatment is laser treatment or heat treatment; and

when the heating treatment is the laser treatment, in the third doped layer, a conductivity type of a region directly irradiated by laser is the same as the conductivity type of the first doped layer.

Further, in the third doped layer, the region whose conductivity type is the same as the conductivity type of the first doped layer extends through the third doped layer in a thickness direction.

Further, a second semiconductor layer is formed on the surface of the side of the first doped layer facing away from the semiconductor substrate and the first surface of the semiconductor substrate not covered by the first doped layer; and

under the heating treatment, the second dopant is diffused into the second semiconductor layer, and due to a high temperature, the first dopant in the first doped layer is also diffused into the second semiconductor layer on the first doped layer, to transform the second semiconductor layer on the first doped layer into the third doped layer and transform the second semiconductor layer on the first surface of the semiconductor substrate into the second doped layer.

Further, in the third doped layer, conductivity types of at least some regions close to the first doped layer are the same as the conductivity type of the first doped layer.

Further, before the third doped layer is formed, in the first doped layer, a peak doping concentration of the first dopant ranges from 1×10atoms/cmto 5×10atoms/cm.

Further, after the third doped layer is formed, in the first doped layer, a doping concentration of the first dopant is greater than a doping concentration of the second dopant; and in the at least some regions in the third doped layer, a doping concentration of the first dopant is greater than a doping concentration of the second dopant.

Further, in the first doped layer, a peak doping concentration of the first dopant ranges from 1×10atoms/cmto 3×10atoms/cm;

Further, a heating peak temperature of the heating treatment is 850° C. or higher, preferably 900° C. or higher, and more preferably 1000° C.; and a heating duration is 10 min or longer at the peak temperature.

Further, during formation of the third doped layer, due to the high temperature, the first dopant and the second dopant in the first doped layer and the third doped layer are diffused into the semiconductor substrate to form a third doped region; and/or

Further, the first dopant is a Group-VA element or a Group-IIIA element, and the second dopant is a Group-VA element or a Group-IIIA element; and preferably, the first dopant is a Group-VA element, and the second dopant is a Group-IIIA element.

Further, before the third doped layer is formed, the method further includes: performing etching on the first doped layer and the second doped layer located at a junction of the second doped layer and the first doped layer on the first surface of the semiconductor substrate, to expose the first surface of the semiconductor substrate and provide an isolation region between the first doped layer and the second doped layer.

Further, after the third doped layer is formed, the method further includes the following step: performing etching on the first doped layer, the second doped layer, and the third doped layer located at a junction of the second doped layer and the first doped layer on the first surface of the semiconductor substrate, to expose the first surface of the semiconductor substrate and provide an isolation region between the first doped layer and the second doped layer.

Further, each of the first doped layer, the second doped layer, and the third doped layer is one of a doped polysilicon layer, a doped microcrystalline silicon layer, or a doped amorphous silicon layer.

The present disclosure provides a solar cell, including a semiconductor substrate, where a first doped layer and a second doped layer are arranged on a first surface of the semiconductor substrate, and a third doped layer is arranged on a surface of a side of the first doped layer facing away from the semiconductor substrate, where

Further, a thickness of the first doped layer ranges from 50 nm to 300 nm; and

a thickness of the third doped layer and a thickness of the second doped layer are the same and are both less than or equal to 150 nm.

Further, when the thickness of the third doped layer is less than or equal to 30 nm, conductivity types of all regions in the third doped layer are the same as the conductivity type of the first doped layer.

Further, the thickness d of the third doped layer is greater than 30 nm and less than or equal to 150 nm, in the third doped layer, conductivity types of at least some regions close to the first doped layer are the same as the conductivity type of the first doped layer.

Further, the thickness of the third doped layer is greater than 30 nm and less than or equal to 150 nm, in the third doped layer, the regions whose conductivity types are the same as the conductivity type of the first doped layer run through the third doped layer in a thickness direction.

Further, in the first doped layer, a doping concentration of the first dopant first increases and then decreases and a doping concentration of the second dopant gradually decreases, both in a direction from a surface of a side away from the semiconductor substrate to a surface of a side close to the semiconductor substrate.

Further, in the second doped layer, a doping concentration of the second dopant remains consistent in a direction from a surface of a side away from the semiconductor substrate to a surface of a side close to the semiconductor substrate.

Further, in the third doped layer, a doping concentration of the first dopant gradually increases in a direction from a surface of a side away from the semiconductor substrate to a surface of a side close to the semiconductor substrate; and

Further, the third doped layer not only covers the surface of the side of the first doped layer facing away from the semiconductor substrate, but also covers a side surface of the first doped layer close to the second doped layer, and the third doped layer covering the surface of the side of the first doped layer is in contact with the second doped layer.

Further, the solar cell further includes a first interface layer, where the first interface layer is located between the semiconductor substrate and the first doped layer; and/or

Further, a width of the first doped layer is the same as a width of the third doped layer, and an isolation region is provided between the first doped layer and the second doped layer and between the third doped layer and the second doped layer.

Further, the solar cell further includes a first interface layer, where the first interface layer is located between the semiconductor substrate and the first doped layer; and/or

Further, the solar cell further includes a first electrode and a second electrode, where the first electrode extends through the back passivation layer to form contact with the regions in the third doped layer whose conductivity type is the same as the conductivity type of the first doped layer; and the second electrode extends through the back passivation layer to form contact with the second doped layer.

Further, the solar cell is fabricated by using the method described above.

According to the present disclosure, in some implementations, a method of fabricating a solar cell includes performing patterning once only to complete fabrication of doped semiconductors in two regions. In some implementations, doped regions have passivated contact structures at both electrodes, bringing a good passivation effect and greatly reducing a recombination rate in metal regions, thereby improving the efficiency of the solar cell. In some implementations, high-temperature heat treatment needs to be performed once only in the back contact fabrication method, reducing thermal damage caused by the high-temperature heat treatment.

—semiconductor substrate,—first interface layer,—first doped layer,—second interface layer,—third doped layer,—second doped layer,—back passivation layer,—first electrode,—second electrode,—isolation region,—third doped region,—fourth doped region,—semiconductor substrate,—first tunnel oxide layer,—second tunnel oxide layer,—third tunnel oxide layer,—first semiconductor layer,—second semiconductor layer,—third semiconductor layer,—first mask layer,—second mask layer,—first doped region,—second doped region,—passivation layer,—first electrode,—second electrode,—first region,—second region, and—isolation region.

Exemplary embodiments of the present disclosure are described below, and various details of the embodiments of the present disclosure are included to facilitate understanding and should be considered exemplary only. Therefore, a person of ordinary skill in the art should be aware that various changes and modifications may be made to the embodiments described here without departing from the scope and spirit of the present disclosure. Similarly, for clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description. In the present disclosure, upper and lower positions are determined according to an incident direction of light, and an incident point of the light is defined as an upper position.

The present disclosure provides two solar cells. Details are as follows:

As shown in, a first solar cell includes a semiconductor substrate, where a surface of a side of the semiconductor substrateis divided into a first region and a second region. A first interface layer, a first doped layer, a second interface layer, and a third doped layerare sequentially arranged on the surface of the side of the semiconductor substratein the first region. A second interface layerand a second doped layerare sequentially arranged on the surface of the same side of the semiconductor substratein the second region. The second interface layerextends from a surface of a side of the first doped layerto a side surface of the first doped layer and covers the semiconductor substratein the second region.

In some implementations, the third doped layernot only covers the second interface layeron a side of the first doped layerfacing away from the semiconductor substratebut also covers a side surface of the first doped layer close to the second doped layer. The third doped layerextending to the side surface is in contact with the second doped layer. As such, the third doped layerarranged between the first doped layerand the second doped layercan be used as a soft breakdown path to provide anti-hot spot effect for the solar cell. A hot spot can refer to a high-temperate area in the solar cell, which may degrade performance or cause damage to the solar cell.

A back passivation layercovering the third doped layerand the second doped layeris further arranged on a surface of a side of the third doped layerfacing away from the second interface layer, and a first electrodeextending through the back passivation layerto form contact with the third doped layeris further arranged on the back passivation layeron the third doped layer. A conductivity type of the first doped layeris opposite to a conductivity type of the second doped layer. Conductivity types of at least some regions in the third doped layerare the same as the conductivity type of the first doped layer. In the third doped layer, a region whose conductivity type is the same as the conductivity type of the first doped layeris a first conductivity type region, and a region whose conductivity type is the same as the conductivity type of the second doped layer is a second conductivity type region. The first electrodeis in contact with the first conductivity type region in the third doped layerand the first electrode is electrically connected to the first doped layerthrough the first conductivity type region, and a second electrodeextending through the back passivation layerto form contact with the second doped layeris further arranged on the back passivation layeron the second doped layer.

The first electrodeand the second electrodemay be both made of a material including gold, silver, or aluminum.

The semiconductor substratemay be a silicon substrate or a germanium substrate.